A powder method for the high-efficacy measurement of electro-optic coefficients

August 21, 2020

Electro-optic crystal shows great promise for extensive applications in laser, optoelectronics, and optical communication, such as high-speed E-O switch, modulator, deflector, laser mode-locking, photoetching, laser radar (LIDAR) and so on. With the prosperous development of Terahertz (THz) spectroscopy technique, E-O crystals are employed in this realm for generation and detection of the THz electromagnetic radiation. Although there are some commercial E-O crystals available in the market, further exploration of novel E-O crystals with superior properties is also in great demand for a variety of current applications. However, the discovering of novel electro-optic crystals is sporadic due to lack of theoretical method for the evaluation of E-O effect and the difficulties of large-sized crystal growth for electro-optic coefficient measurement. Hence, the strategy for exploration of novel E-O crystals should be improved.

Herein, to address such an issue, inspired by the well-known powder second harmonic generation (SHG) technique reported by Kurtz and Perry (J. Appl. Phys. 39, 3798 (1968). Times Cited: 4176) who open a highway for the exploration new NLO crystals, a high-efficacy evaluation method using accessible powder samples is proposed, in which second harmonic generation effect, infrared reflectance spectrum, and Raman spectrum are introduced to predict the magnitude of electro-optic coefficient. Particularly, the evaluation method is established on the material in powder form or small crystals in micron size, which can be easily obtained at the onset of experiment. Comparing to traditional method for the measurement of E-O coefficients with large-sized crystal which is difficult and time-consuming, the utilization of powders renders the exploring process to be more efficient.

The calculated electro-optic coefficients of numerous reported electro-optic crystals through this approach give universally agreement with the experimental values, evidencing the validity of strategy. Based on this method, CsLiMoO¬4 is screened as a novel electro-optic crystal and high-quality crystal is grown by the Czochralski technique for electro-optic coefficient measurement with half-wave voltage method, whose result is also comparable to the calculated value. Also, on account of the preferable calculated E-O coefficient and the relationship between E-O effect and macroscopic symmetry of crystal, CLM was selected as a potential E-O crystal. Consequently, this powder method for the evaluation of E-O crystals is not only significant for the further understanding of the E-O coefficient, but also have important implications for the high-efficacy screening of promising E-O crystals. The powder evaluation strategy presented in this work will pave a new avenue to explore promising electro-optic crystals efficiently.
See the article:

Feng Xu, Ge Zhang, Min Luo, Guang Peng, Yu Chen, Tao Yan* and Ning Ye*
A powder method for the high-efficacy evaluation of electro-optic crystals
Natl Sci Rev 2020, DOI: 10.1093/nsr/nwaa104

The National Science Review is the first comprehensive scholarly journal released in English in China that is aimed at linking the country's rapidly advancing community of scientists with the global frontiers of science and technology. The journal also aims to shine a worldwide spotlight on scientific research advances across China.

Science China Press

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